38 
PROFESSOR P. M. DUNCAN ON THE PEESISTENCE OF 
type ; others have the hexameral arrangement, and Moiitlivaltia Murchisonice, Dune., 
has its septa collected together in four systems. All the species have epithecate walls. 
In the zone of Ammonites Bucklandi the genus Lepidophyllia has a very rugose 
facies; and Montlivaltia radiata. Dune., of the zone of Ammonites raricostatus, is 
evidently furnished with a septal arrangement on the tetrameral type, the four principal 
septa being very large. Even in the Middle Lias, Lepidophyllia hebridensis, Dune., has 
a rugose aspect ; and the greatest of all Montlivaltia % the Montlivaltia Victorias, of the 
zone of Ammonites Henleyi, has an epithecate wall, although there are six systems of 
septa. 
Thus from the Rhaetic beds to the Middle Liassic strata the examples of more or less 
modified rugose types are frequent ; for the species with the decameral septal arrange- 
ment very probably originated from forms of Rugosa with indefinite septal numbers. 
After the age of the Lias to the Tertiary period the septal arrangements of many species 
and subgenera appear to be very confused ; but still many rugose types persisted, having 
the tetrameral disposition or the decameral ; so that if it is admitted (and it may be so 
consistently with exact truth) that some of the Triassic corals, especially the Montlivaltice, 
have certain but rather faint rugose characters, there is evidence that there has not been 
a marked break in the continuity of coral life. 
Doubtless many species have varied and have recurred to their ancestral forms; and 
this may account for the appearance of tetrameral or octomeral types late in the world’s 
history in genera whose older secondary species were of the hexameral type ; but the 
persistence of the rugose type, more or less modified, up to the present day can no longer 
be denied. 
Probably many genera with hexameral septal arrangements originated in Palaeozoic 
times; and I have noticed in a former communication* the interesting relation of the 
Carboniferous Heterophyllice and the Devonian Battersbyice to the corals of the normal 
Neozoic type. 
VII. It is very remarkable that the two recent species of Rugosa, R aplophy Uia par a- 
doxa , Pourtales, and Gu.ynia annulata, Duncan, should belong to the same family of 
the section, and that the tertiary Conosmilioe with Palaeozoic affinities should of necessity 
be included in a closely allied family of the Rugosa. 
That the American and Mediterranean species should be closely allied is in keeping 
with the results of the study of the distribution of deep-sea as well as of shallow-water 
forms in those distant localities. The Hippurite limestones of Jamaica contain the same 
species of Madreporaria as the Cretaceous rocks of Gosau in Austria ; the dark Eocene 
shales of the same island have yielded the same species of Madreporaria as the early 
Tertiary deposits of North-western Europe; the Miocene fauna of the Caribbean islands 
contains the characteristic species of the corresponding Falunian deposits of France, Italy, 
and Malta; and even the recent Algae of part of the West-Indian area resemble those 
* Philosophical Transactions, 1867, p. 643. 
